find the larger file size

#find /var -size +10M  -mount -exec du -h {} \; | less

rescue mode to recover the grub

1. Type 'linux rescue' at the boot prompt.
2. After the command prompt is displayed, change the root directory to the OS installation by typing the following command:

# chroot /mnt/sysimage
Manually install grub using
#grub-install /dev/cciss/c0d0

ISCSI Multipathed scan disk and add the disk to VG to extend the file system in Redhat 5.6

How to scan for newly added disks/luns?

- rescan-scsi-bus.sh  [Redhat Genuine utility]

- if hp tools are installed then use command  hp_rescan -h  for scanning new lun

#rescan-scsi-bus.sh
Host adapter 0 (ata_piix) found.
Host adapter 1 (ata_piix) found.
Host adapter 2 (lpfc) found.
Host adapter 3 (lpfc) found.
Scanning SCSI subsystem for new devices
Scanning host 0 for  SCSI target IDs  0 1 2 3 4 5 6 7, all LUNs
Scanning for device 0 0 0 0 ...
OLD: Host: scsi0 Channel: 00 Id: 00 Lun: 00
      Vendor: TEAC     Model: DV-28S-W         Rev: C.2D
      Type:   CD-ROM                           ANSI SCSI revision: 05
Scanning host 1 channels  0 for  SCSI target IDs  0 1 2 3 4 5 6 7, all LUNs
Scanning host 2 for  all SCSI target IDs, all LUNs
Scanning for device 2 0 0 0 ...
OLD: Host: scsi2 Channel: 00 Id: 00 Lun: 00
      Vendor: HP       Model: OPEN-V           Rev: 6006
      Type:   Direct-Access                    ANSI SCSI revision: 03
Scanning for device 2 0 1 0 ...
OLD: Host: scsi2 Channel: 00 Id: 01 Lun: 00
      Vendor: HP       Model: OPEN-V           Rev: 6006
      Type:   Direct-Access                    ANSI SCSI revision: 03
Scanning for device 2 0 2 0 ...
OLD: Host: scsi2 Channel: 00 Id: 02 Lun: 00
      Vendor: HP       Model: OPEN-V           Rev: 6006
      Type:   Direct-Access                    ANSI SCSI revision: 03
Scanning host 3 for  all SCSI target IDs, all LUNs
Scanning for device 3 0 0 0 ...
OLD: Host: scsi3 Channel: 00 Id: 00 Lun: 00
      Vendor: HP       Model: OPEN-V           Rev: 6006
      Type:   Direct-Access                    ANSI SCSI revision: 03
Scanning for device 3 0 1 0 ...
OLD: Host: scsi3 Channel: 00 Id: 01 Lun: 00
      Vendor: HP       Model: OPEN-V           Rev: 6006
      Type:   Direct-Access                    ANSI SCSI revision: 03
Scanning for device 3 0 2 0 ...
OLD: Host: scsi3 Channel: 00 Id: 02 Lun: 00
      Vendor: HP       Model: OPEN-V           Rev: 6006
      Type:   Direct-Access                    ANSI SCSI revision: 03
0 new device(s) found.-----------------------------------> Newly added devices
0 device(s) removed.-------------------------------> newly removed devices.
#
List all supported fibre channel HBAs

#hp_rescan -l
QLogic adapters:

Emulex adapters:

/sys/class/scsi_host/3
/sys/class/scsi_host/2

Brocade adapters:

#

#hp_rescan -a -----> will show what are the host adapters are used for the disks, here host0 & host1
Rescanning /sys/class/scsi_host/host0
Rescanning /sys/class/scsi_host/host1
#

# adapter_info -l
sda    3,0,0,0          HP OPEN-V 6008
sdb    3,0,1,0          HP OPEN-V 6008
sdc    3,0,2,0          HP OPEN-V 6008
sdd    2,0,0,0          HP OPEN-V 6008
sde    2,0,1,0          HP OPEN-V 6008
sdf    2,0,2,0          HP OPEN-V 6008

sg1   3,0,0,0         HP OPEN-V 6008
sg2   3,0,1,0         HP OPEN-V 6008
sg3   3,0,2,0         HP OPEN-V 6008
sg4   2,0,0,0         HP OPEN-V 6008
sg5   2,0,1,0         HP OPEN-V 6008
sg6   2,0,2,0         HP OPEN-V 6008
#

Execute the below command to get the DM disks:

multipath -ll

mpath0 (360060e800571e700000071e700006021) dm-10 HP,OPEN-V
[size=102G][features=1 queue_if_no_path][hwhandler=0][rw]
\_ round-robin 0 [prio=2][active]
 \_ 3:0:3:0 sdi 8:128 [active][ready]
 \_ 2:0:3:0 sdk 8:160 [active][ready]

-------> here the sdi & sdk are the alternate paths which forms the "mpath0"

Allocate the total disk space to Primary partation 1

#fdisk /dev/mapper/mpath0
select n() to create the new partation
Select Primary partation
select 1
Enter to take the default(total space allocation)
select w(write) to save the created partation

Scan the newly added device and update the modified permission to Kernel

#partprobe

use the kpartx utility creates the device maps from partition tables

#kpartx -a /dev/mapper/mpath0

create the physical volume with lable information

#pvcreate /dev/mapper/mpath0p1

Extend the VG

#lvextend -L +100g /dev/mapper/vg-u01
 Extending logical volume u03 to 200.00 GB
 Logical volume u01 successfully resized
#

resize the file system

# resize2fs /dev/mapper/vg-u01
resize2fs 1.39 (29-May-2006)
Filesystem at /dev/mapper/vg-u01 is mounted on /u01; on-line resizing required
Performing an on-line resize of /dev/mapper/vg-u01 to 52428800 (4k) blocks.
The filesystem on /dev/mapper/vg-u01 is now 52428800 blocks long.
#

Extend the root file system in Redhat Linux 5.6

Extend the LV(Logical Volume)

root@node ~]# lvextend -L 12g /dev/mapper/rvg-rootlv
  Extending logical volume rootlv to 12.00 GB
  Logical volume rootlv successfully resized
[root@node ~]#

Grow the file system

[root@node ~]# resize4fs -p /dev/mapper/rvg-rootlv
resize4fs 1.41.12 (17-May-2010)
Filesystem at /dev/mapper/rvg-rootlv is mounted on /; on-line resizing required
old desc_blocks = 1, new_desc_blocks = 1
Performing an on-line resize of /dev/mapper/rvg-rootlv to 3145728 (4k) blocks.
The filesystem on /dev/mapper/rvg-rootlv is now 3145728 blocks long.
[root@node ~]#

Check the file system status
[root@node ~]# df -h /
Filesystem            Size  Used Avail Use% Mounted on
/dev/mapper/rvg-rootlv
                       12G  3.1G  7.6G  29% /
[root@node ~]#